Being excellent in photographic properties such as sensitivity and gradation as compared to other photographic processes such as electrophotography and a diazo process, a photographic process using silver halide has been most widely used. In recent years, a technique for providing images in a rapid and simple manner has been developed by changing the image formation process of light-sensitive materials using silver halides from a wet process using, e.g., a conventional developer to a dry process, e.g., by heating.
A heat-developable light-sensitive material is known in the art. Examples of the heat-developable light-sensitive material and its process are described in SHASHINKOGAKU NO KISO (Fundamentals of Photographic Engineering) (published by Corona, pp. 553-555, 1977), EIZO JOHO (Image Information) (published in April 1978, page 401), Handbook of Photography and Reprography (edited by Neblets, 7th edition, pp. 32-33, published by Van Nostrand Reinhold Company), U.S. Pat. Nos. 3,152,904, 3,301,678, 3,392,020 and 3,457,075, British Pat. Nos. 1,131,108 and 1,167,777, and Research Disclosure, RD No. 17029 (June 1978, pp. 9-15).
Examples of a process for obtaining color images by heating are proposed in Research Disclosure, RD No. 16966 (May 1978, pp. 54-58), Research Disclosure, RD No. 14433 (April 1976, pp. 30-32), U.S. Pat. Nos. 3,985,655, 4,463,079, 4,474,867, 4,478,927, 4,507,380, 4,500,626 and 4,483,914. All these processes are designed to produce or release a dye, thereby forming an imagewise distribution of the dye. These processes are characterized in that they can provide an imagewise distribution of the dye in a short period of time.
In a process which comprises heating the light-sensitive element in the presence of at least one of a base and a base precursor (abridged "a base and/or base precursor") to form an imagewise distribution of a mobile dye, and transferring and fixing the imagewise distribution of a mobile dye to a dye fixing element, the heat development and the dye transfer may be effected simultaneously or in succession, or the two processes may be separately effected. It is desired that the speed of development and transfer be further increased in the former case and the speed of transfer be further increased in the latter case in order to obtain an imagewise distribution of a dye in a short period of time.
If a base and/or base precursor is incorporated in the dye fixing element, a binder used in the dye fixing element such as gelatin decomposes when acted upon by the base with the passage of time. As a result, when the dye fixing element is peeled off the light-sensitive element, the coated layer of the dye fixing element is peeled off.